From 69787793e7f0673465c89714d1522fde978bbfa8 Mon Sep 17 00:00:00 2001 From: Huacai Chen Date: Tue, 18 Jun 2024 16:13:36 +0800 Subject: [PATCH] cpu: Fix broken cmdline "nosmp" and "maxcpus=0" commit 6ef8eb5125722c241fd60d7b0c872d5c2e5dd4ca upstream. After the rework of "Parallel CPU bringup", the cmdline "nosmp" and "maxcpus=0" parameters are not working anymore. These parameters set setup_max_cpus to zero and that's handed to bringup_nonboot_cpus(). The code there does a decrement before checking for zero, which brings it into the negative space and brings up all CPUs. Add a zero check at the beginning of the function to prevent this. [ tglx: Massaged change log ] Fixes: 18415f33e2ac4ab382 ("cpu/hotplug: Allow "parallel" bringup up to CPUHP_BP_KICK_AP_STATE") Fixes: 06c6796e0304234da6 ("cpu/hotplug: Fix off by one in cpuhp_bringup_mask()") Signed-off-by: Huacai Chen Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240618081336.3996825-1-chenhuacai@loongson.cn Signed-off-by: Greg Kroah-Hartman --- kernel/cpu.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/cpu.c b/kernel/cpu.c index 7ef4bc17453c..874bfb952e6e 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1907,6 +1907,9 @@ static inline bool cpuhp_bringup_cpus_parallel(unsigned int ncpus) { return fals void __init bringup_nonboot_cpus(unsigned int setup_max_cpus) { + if (!setup_max_cpus) + return; + /* Try parallel bringup optimization if enabled */ if (cpuhp_bringup_cpus_parallel(setup_max_cpus)) return;